Shock chemistry in the molecular clouds associated with SNR IC 443

Several interstellar molecules have been detected toward the highly perturbed B and G clouds associated with the supernova remnant IC 443 via their 3 mm transitions, including N2H+, SiO, SO, CN, HNC, and H13CO+. The (J, K) = (1, 1) and (2, 2) inversion lines of metastable ammonia have also been observed, as well as the J = 3-2 transition of HCO+ at 1.2 mm. Analysis of the (1, 1) and (2, 2) inversion lines of NH3 indicates minimum gas kinetic temperatures of TK = 70 K toward cloud B, and TK = 33 K in cloud G. Modeling of the J = 1-0 and J = 3-2 transitions of HCO+ implies densities greater than 10(5) cm-3 toward both positions. These data clearly show that hot and dense material is present in IC 443, and they suggest the presence of shocks in both regions. A careful analysis of the HCO+ lines indicates that the HCO+ abundance is at most enhanced by factors of a few over that found in cold, quiescent gas. This conclusion contradicts past claims of HCO+ abundance enhancements of several orders of magnitude in the perturbed regions. The N2H+ abundance was also found to be similar to that in cold gas, suggesting that there is no increase in ionization in the clouds. The abundances of SO and CS, as well as CN and NH3, do not appear to differ significantly from those found in cold dark clouds, although chemistry models predict sulfur-containing species to undergo high-temperature enhancements. SiO, however, is found to have an abundance in the perturbed gas 100 times larger than the upper limits observed in the dark cloud TMC 1, a result in agreement with high temperature chemistry models. In addition, the HNC/HCN ratio in both IC 443 B and G was found to be approximately 0.1--far from the ratio of 1 predicted by low-temperature ion-molecule chemistry, but similar to the values observed in clouds where elevated temperatures are present.     

Genetic diversity and population structure of the franciscana dolphin,Pontoporia blainvillei,in Southern Buenos Aires,Argentina

The franciscana dolphin, Pontoporia blainvillei, is endemic to the coastal waters of the southwestern Atlantic Ocean and the most endangered dolphin in the area. Four Franciscana Management Areas (FMAs) are currently recognised; however, results of genetic studies suggest the requirement for additional FMAs and highlight the need for more detailed studies in the southern extreme of the species distribution. With this aim, we studied the genetic diversity and population structure of the species analysing an mtDNA control region fragment (434?bp) in 44 individuals collected in four sampling sites located in Southern Buenos Aires. Haplotype diversity (H?=?0.75?±?0.05) was mostly higher than the observed in endangered or near threatened odontocetes. Population structure analyses suggest that three different genetic populations should be recognised within FMA IV: Northern, Eastern and Southern Buenos Aires. Altogether, these results should be taken into account in future conservation plans for the species.     

Noble gases and chemical composition of Shergotty mineral fractions,Chassigny, and Yamato 793605: The trapped argon-40/argon-36 ratio and ejection times of Martian meteorites

Abstract— We report the elemental and isotopic composition of the noble gases as well as the chemical abundances in pyroxene, maskelynite/mesostasis glass, and bulk material of Shergotty and of bulk samples from Chassigny and Yamato 793605. The ⁴⁰K-⁴⁰Ar isochron for the Shergotty minerals yields a gas retention age of 196 Ma, which is, within errors, in agreement with previously determined Rb-Sr internal isochron ages. Argon that was trapped at this time has a ⁴⁰Ar/³⁶Ar ratio of 1100. For Chassigny and Y-793605, we obtain trapped ⁴⁰Ar/³⁶Ar ratios of 1380 and 950, respectively. Using these results and literature data, we show that the three shergottites, Shergotty, Zagami, and QUE 94001; the lherzolites ALH 77005, LEW 88516, and Y-793605; as well as Chassigny and ALH 84001 contain a mixture of Martian mantle and atmospheric Ar; whereas, the trapped ⁴⁰Ar/³⁶Ar ratio of the nakhlites, Nakhla, Lafayette, and Governador Valadares cannot be determined with the present data. We show that Martian atmospheric trapped Ar in Martian meteorites is correlated with the shock pressure that they experienced. Hence, we conclude that the Martian atmospheric gases were introduced by shock into the meteoritic material. For the Shergotty minerals, we obtain ³He-, ²¹Ne-, and ³⁸Ar-based cosmic-ray exposure ages of 3.0 Ma, and for the lherzolite Y-793605, 4.0 Ma, which confirms our earlier conclusion that the lherzolites were ejected from Mars ～1 Ma before the shergottites. Chassigny yields the previously known ejection age of 11.6 Ma.     

海拉尔盆地基底晚古生代adakite的发现及其地质意义

海拉尔盆地的前中生代基底隶属中亚造山带东段的兴蒙造山带。 在盆地基底地层中发现了具有adakite成分特征的粗面安山岩、英安岩和闪长玢岩。 这些火成岩与晚古生代沉积地层交互或伴生, 共同构成晚中生代裂陷盆地的基底。 地球化学研究表明, 这些火成岩基本上属于高钾钙碱性和准铝质岩石系列, 具有高SiO₂和Al₂O₃含量, 高Sr、Sr/Y和La/Yb值, 富集轻稀土(LREE), 亏损重稀土(HREE)、Y和高场强元素(HFSE),Eu表现弱的负异常或轻微的正异常, 相容元素Mg、Cr和Ni含量低, 这些特征与增厚下地壳部分熔融成因的adakite非常相似, 而明显不同于典型的由俯冲洋壳熔融形成的adakite。 样品的(⁸⁷Sr/⁸⁶Sr)_i值基本一致,为0.7041, (¹⁴³Nd/¹⁴⁴Nd)_i值为0.51243~0.51247, ε_Nd (t)为正值(+3.7~+4.5), 显示其岩浆源区可能源于弱亏损地幔, 或亏损地幔受到地壳物质混染。 本文认为海拉尔地区晚古生代adakite型岩浆很可能是由当时新底侵的玄武质下地壳在角闪岩相向榴辉岩相过度或榴辉岩相条件下部分熔融形成。 这些adakite岩石的出现反映了兴蒙造山带晚古生代受到了古亚洲洋的俯冲消减引起的强烈的地幔玄武质岩浆底侵作用, 并由此导致地壳垂向上显著的增生加厚过程。     

阿尔泰造山带富蕴基性麻粒岩折返过程:来自裂变径迹热年代学的限定

论文在阿尔泰造山带富蕴县乌恰沟基性麻粒岩的锆石SHRIMP年代学、地球化学、变质温压条件和形成的大地构造背景研究基础上,利用麻粒岩、围岩片麻岩和侵入到麻粒岩的辉绿岩岩墙的裂变径迹热年代学探讨了麻粒岩从深部折返至地表的过程。裂变径迹年代学研究发现基性麻粒岩的锆石裂变径迹年龄为三叠纪,而麻粒岩、围岩片麻岩和侵入到麻粒岩的辉绿岩岩墙的磷灰石裂变径迹年龄均显示为晚白垩世至新生代早期。对磷灰石裂变径迹测试所得到的径迹长度和单颗粒年龄数据进行热史模拟表明,三叠纪时,基性麻粒岩抬升至约地表以下7.8km的上地壳,温度冷却至锆石裂变径迹的封闭温度;晚白垩世至新生代早期(约100～50Ma),麻粒岩、围岩片麻岩和辉绿岩抬升至约地表以下3.5km,温度冷却至磷灰石裂变径迹的封闭温度;约50～15Ma,三者滞留在约地表以下1.7km的磷灰石部分退火带;约15Ma以来,喜马拉雅运动使得它们被抬升剥蚀至地表。     

Age verification,growth and life history of rubyfish Plagiogeneion rubiginosum

Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (¹⁴C) and stable isotope (δ¹⁸O and δ¹³C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core ¹⁴C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the ¹⁴C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ¹⁸O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ¹³C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns.     

Rotation velocity and neutral hydrogen distribution dependency on magnetic field strength in spiral galaxies

The rotation velocity of a simulated plasma galaxy is compared to the rotation curves of Sc type spiral galaxies. Both show flat rotation curves with velocities of the order of several hundred kilometers per second, modified by E × B instabilities. Maps of the strength and distribution of galactic magnetic fields and neutral hydrogen regions, as-well-as as predictions by particle-in-cell simulations run in the late 1970s, are compared to Effelsberg observations.Agreement between simulation and observation is best when the simulation galaxy masses are identical to the observational masses of spiral galaxies. No dark matter is needed.